Saturday, October 26, 2013

How to Ban the Brown Out Enable

ERIE BROWN MATTER IS YOUR GREATEST FEAR when trying to operate your Parallax Propeller chip from batteries. You never know when the the battery powering the chip will reach the fatal 2.7 volt rest level, and brown matter will erase the entire functioning RAM data of the chip and cause a fatal reboot! Brown matter - you can cuss at it, but we suggest a better approach...

STOP your Propeller processor from that annoying reset when the power supply voltage goes down around 2.7 volts when battery power is diminished.
Updated schematic with BOEn disabled and chip improvements in place


BAN BROWNOUT! Follow the schematic and connect BOEn to VDD, and run a 220 ohm resistor from RESn to VDD, to disable the BOE Brown Out Enable. The Propeller chip may now continue to function when the voltage drops down to and below 2.7 volts. This can be useful when the Propeller is running in lower power modes, for example, with the clock set to RC Slow or RC Fast, or when a battery operated circuit dips in its battery energy supply cycle before recharging.

I can't seem to disable brown out detection, if I connect BOEn to Vdd even at 3.3v the Prop won't do anything.
Put an external pullup on RST (a 220 ohm resistor from RST to VDD). When BOE Brown Out Enable is grounded, the Propeller chip has an internal pullup activated. When BOE is held high, the internal pullup is not active, and an external pullup is required on RST to restore functioning.